Impact craters,
like those we observe on the Moon, also occur on Earth. They result
from the collisions of extraterrestrial bodies -- like meteorites,
asteroids or comets -- with the Earth. Planetary scientists study
Earth's impact craters to gain insight about the early history of
the Earth and the Solar System. Recent studies indicate that large
impacts on Earth may have played an important role in the succession
of life on Earth.

Australia is
a very good place to observe and study impact craters. Much of the
Australian surface is very old, so Australia has collected more
impacts than many other parts of the world. The craters aren't weathered
quickly or hidden by dense vegetation because of the dry climate.

This image
shows Gosses Bluff, an impact crater sandwiched between the MacDonnell
Range to the north and the James Range to the south in Australia's
Northern Territory -- it is about 160 kilometers (99 miles) west
of Alice Springs. It is one of the most studied of the Australian
impact craters. The impactor, an asteroid or comet, was probably
about 1 kilometer (0.6 miles) in diameter and crashed into the Earth
about 142 million years ago. The isolated circular feature within
the crater consists of a central ring of hills about 4.5 kilometers
(2.8 miles) in diameter. The grayish feature surrounding the inner
ring probably marks the original boundary of the outer rim.

Astronaut
photograph ISS007-E-05697
was taken with an Electronic Still Camera on May 20, 2003 with a
180-mm lens and is provided by the Earth Sciences and Image Analysis
Laboratory at Johnson Space Center. Additional images taken by astronauts and cosmonauts can be viewed at the NASA-JSC Gateway
to Astronaut Photography of Earth.